Can a gantry crane move on a rail sleeper?

A gantry crane could move on rails mounted on railway sleepers. However, one would need to be very careful that the sleepers do not move so as to cause the rails to move relative to each other, and the crane falls off the rails. That would be somewhere between unfortunate and disastrously tragic. For that reason, it is more usual to mount the rails either in or on a concrete slab or series of large slabs.